1. Field of the Invention:
This invention relates generally to multiple speed epicyclic or planetary transmissions housed within the rear hub of chain driven bicycles in addition to a modification of a conventional bicycle frame which permits the chain to be fully enclosed.
2. Description of the Prior Art:
Multiple speed bicycles commonly use either a chain and derailleur system with ten to fifteen speeds, or a chain driven rear hub providing three speeds with a single epicyclic gear train, and four to seven speeds with a pair of co-operating epicyclic gear trains. The U.S. patent to Hillyer, No. 3,934,493, provides seven speeds with two co-operating epicyclic gear trains but requires six one way clutches and a complicated shift mechanism which makes it too costly to compete with bicycles using the chain and deraileur system. On all chain driven bicycles the chain must be kept reasonably clean and well oiled for efficient operation and to prevent premature chain failure and chain maintenance becomes particularly troublesome if the bicycle is ridden extensively on dirt roads and trails. With the current popularity of off-road and mountain bicycles, a sealed chain drive is needed to mininmize the maintenance problem with a bicycle which can serve for commuting as well as off-road recreation riding. An object of the present invention is to provide an enclosed chain drive which essentially eliminates chain maintenance coupled with an improved multiple speed planetary transmission sealed in a gear case within the rear hub, with a range of speeds comparable to ten speed chain and derailleur touring bicycles.